FUNCTIONAL INGREDIENTS
Microfibrillated cellulose: stability without viscosity
Ellie Copsey – Sappi
Across all areas of personal care, consumers are loving ultra-thin textures. In both the US and UK, fluid and serum textures are the top selling face sunscreen format, and in skin care with milky toners having been a key part of 2024 launches, milk textures set to make a comeback in 2025.1,2 Emulsions offer many benefits, including
the ability to combine water-soluble and oil-soluble actives into a single system, with improved moisturisation and play time on the skin over water-based systems, as well as significantly improved skin feel and reduced cost compared to anhydrous systems. Emulsions are versatile and can range from
thin fluid lotions to thick rich creams, however, very fluid emulsions are notoriously difficult to stabilise. Reducing emulsifier level can achieve a low viscosity but insufficient emulsifier will ultimately lead to phase separation and poor stability. On the flip side, increasing the emulsifier usage level to obtain stability will often increase viscosity. Polymers are commonly used to stabilise
oil-in-water (O/W) emulsions, either by reinforcing the stabilising layer at the oil-water interface, and/or by increasing viscosity of the continuous phase. Increasing viscosity reduces the mobility of oil droplets, ultimately preventing droplet collision and their resulting coalescence.3 Increasing viscosity of the continuous phase in this way improves long term stability of emulsions, but can have a significant impact
on the flow and skin feel of the formulation that is often undesirable.
Microfibrillated cellulose - a troubleshooting hero Sappi’s Valida S+ range (INCI: Aqua, Cellulose and/or Cellulose Gum), hereafter known as microfibrillated cellulose, is a 99.9% natural (ISO 16128) cellulose material, derived from PEFC and FSC certified wood pulp, sourced from sustainably manged forests. Microfibrillated cellulose is a
multifunctional troubleshooting unsung hero of the formulators toolbox, forming a 3D network throughout a formulation that offers stability without increasing viscosity and can
improve skin feel by reducing tack, reducing greasiness, and providing a silicone-like powdery after feel. Cellulose is the most abundant biopolymer and it gets a lot of attention due
on earth,4
to its naturality and biodegradability profile, while being non-toxic, and highly renewable if sustainably sourced. There are many ways of processing
cellulose, resulting in differing structure and properties, as shown in Table 1. Unlike conventional cellulose materials,
microfibrillated cellulose is produced without any chemical treatment or chemical modification. The purely mechanical fibrillation process results in extremely long, but thin, cellulose fibres which are capable of forming a robust 3D network, stabilised purely by entanglement (Figure 1). Having a solely mechanical process not
only maintains high naturality, but also makes for a robust product that, unlike many entanglement polymers, is not pH dependent. Microfibrillated cellulose is therefore highly tolerant to pH (suitable from pH 2-10+), electrolytes, temperature and additionally cannot be over-sheared. Microfibrillated cellulose is a very robust
multifunctional material, offering many beneficial properties to personal care formulations. Its significantly higher storage modulus compared to rheology modifiers such as xanthan gum and guar gum allows for powerful suspension properties, but its extremely shear thinning and thixotropic (fast
TABLE 1: PROCESSING CELLULOSE IN DIFFERENT WAYS RESULTS IN DIFFERING STRUCTURE AND PROPERTIES Category Chemical
Treatment Acid
Chemical Mechanical Carboxymethylation Grinding Product Microcrystalline Cellulose
Carboxymethylated Cellulose
(INCI: Cellulose Gum)
Ground cellulose (INCI: Cellulose)
Morphology Short, needle-like
Chemically modified cellulose with CH2-COOH groups
Uncontrolled fibre length
65
Properties Rheology modifier Rheology modifier
Limited application in personal care due to variance, can be used for exfoliation
Mechanical Fibrillation
Microfibrillated Cellulose (INCI: Cellulose)
Long fibre length with short diameter resulting in 3D entangled network structure
Multifunctional: ■ Stability without viscosity ■ Suspension ■ Emulsion stabilisation ■ Sensory enhancer ■ Foam booster ■ SPF booster ■ Soft focus effect
www.personalcaremagazine.com April 2025 PERSONAL CARE
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